Twin rotary actuator



April 12, 1960 J. N. TooTLE TWIN ROTARY ACTUATOR Filed May 14. 1959 @N mm 0 E A Nm mm m \W%\\\ a mM IM. Y om, 1H vl Y li m vw mm a W E. v mm Nm J i l //wm m\/ I a IIIII|||| a o: mo. wo. g. om mwwo No Hmwlllwofmom :lmellgwm 2. wm ill A |A 2 2 m K uw :M /w o@ wm xlml IQ.. Ill

wm o QN w. wm mw His Affor/zey iinited States Patent O TWIN ROTARY ACTUATOR James N. Tootle, Troy, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application May 14, 1959, Serial No. 813,208

9 Claims. (Cl. 74-89) tors is oftentimes quite limited. In addition, it is some- |times desirable to provide two control systems for an actuator so that if one of the control systems should become inoperative, the actuator can be operated by the `other control system. The present invention relates to a rotary actuator assembly of the general type disclosed in copending application Serial No. 794,280 'tiled February v19, 1959, in the name of Howard M. Geyer and assigned Ato the assignee of the present invention, including a pair of tandem connected pistons whereby the torque output vof the actuator assembly is substantially twice that of a ,conventional actuator assembly of the same diameter. in addition, the actuator cylinder and piston assemblies are so arranged to provide twin reliability in that each cylinder and piston assembly can be operated by a separate hydraulic control system. Accordingly, amongmy ob-r jects are the provision of a tw-in rotary hydraulic actuator assembly; the further provision of a rotary actuator assembly including a pair of tandem arranged pistons disposed for movement in separate cylinders; and the -still further provision of a rotary actuator assembly of the 4helical spline type including a centrally located rotary outlet shaft which is drivingly connected to a pair of tandem arranged pistons.

The aforementioned and other objects are accomplished in the present invention by embodying a central annular bulkhead in the cylinder assembly solas to form two cylinderswithin which avpair of tandem connected .reciprocable pistons are disposed. Specifically, the actuator comprises a stationaryl cylinder assembly having a pair of end caps with centrally located bores within which a double ended rotary output shaft 4is journalled. T-he cylinder assembly is divided into two cylinders by an intermediate annular bulkhead. Each cylinder contains a'reciprocable annular piston, each piston dividing its respective cylinder into a pair of opposed chambers. Each piston includes a set of internal helical spline teeth,

and one of the pistons includes an axially extending anf nular skirt which extends through and is sealingly engaged by the bulkhead, and is rigidly connected to the other piston. Accordingly, the pistons are mechanically interconnected for simultaneous movement in the same direction, and are therefore termed tandem connected pistons. l

The cylinder assembly has a sleeve rigidly connected thereto having a set of external helical spline teeth. This lsleeve constitutes a stationary reaction member, and the Iexternal helical spline teeth thereof are engaged by the linternal helical spline teeth on one of. the pistons. The output shaft has a set of external helical splineteeth -whichare engaged by the helical spline teeth on the other piston. The arrangement of parts issuch that reciproca- :tion of the piston is accomplishedby angular movement thereof due to the interaction'of vthe helical spline teeth Y 2,932,206 Fate-:rated Apr. 12, 1960 on the fixed reaction sleeve and the other piston. This angular ymovement of the tandem connection pistons is imparted to the rotary output shaft through the helical spline connection between the other piston and the rotary ouput shaft whereby the rotary output shaft is rotated throughout an angle equal yto the sum of the leads of the helical spline teeth on the xed reaction member of the helical spline teeth on the output shaft.

Each end cap of the cylinder assembly contains a control port for the supply and drain of hydraulic fluid under pressure to one chamber of each cylinder. In -addition, each end cap contains a drain port through which hydraulic Yfluid flows in metered amounts for actuator cooling. In order to provide the metered flow of hydraulic fluid for actuator cooling, each end cap has a pair of metallic piston ring assemblies which engage the rotary output shaft. The piston ring assemblies constitute self-cleaning orifices which permit a metered amount of fluid to ow therethrough due to a pressure differential on opposite sides of the piston rings. The metered cooling iow is collected in an annular groove communicating with the drain ports and cannot escape out ofthe end of the end caps by virtue of low pressure metallic seals. The intermediate annular bulkhead also containsa pair of ports, one of which communicates with 4the inboard chamber of one cylinder, and the other of which communicates with the inboard chamber of the other cylinder. v In an installation where high torque output is required, the ports communicating with the outboard chamber of one cylinder and the inboard chamber of the other cylinder may be interconnected so that substantially twice the area of each piston is simultaneously subjected to a pressure dierential whereby the torque output of the rotary actuator will be substantially twice that of a comparable actuatorof the same diameter containing only asingle piston( In other instances, it may be desirable to provide twin reliability for the actuators, in which instance the inboard and outboard chambers of the other cylinder can be connected to a second control system. One of the control systems can be used during normal operation, and the other control system used only in case of emergency when the normal control system is inoperative. When the actuator is so connected, of'course, the torque output thereof is only substantially 'half as great as the torqueoutput when both pistons are simultaneously subjected to pressure differentials.

Further objects and advantages of the present inven-y tion will be apparent from the following description, reference being had to the accompanying drawing, wherein a preferred embodiment of the present invention is clearly shown.

In the drawing:

l The drawing is a fragmentary longitudinal sectional view of a rotary actuator assembly constructed according to the present invention.

With particular referenceto the drawing, a hydraulically operated rotary actuator is depicted including a sta- Qtionarycylinder assembly 10 comprising a pair of sleeves 12 and 14, the inner ends of which are suitably connected such as by means of welds 16 to an annular bulkhead 18. The .sleeve 12 is connected to an end cap 20 by a torque resisting threaded coupling 22, and the sleeve 14 is connected toan end cap 24 by a threaded coupling 26.. .The end caps 20 and 24 are formed with 'threaded .port openings 28 and 30, respectively.

. .The lend cap Ztl is connected by means of a weld 32 to a sleeve 3,4. The sleeve 34 includes a portion disposed .within the cylinder and is coaxial therewith, the internal portion having a set of external helical spline teeth 36.

y' 'l'l'ic boren'of the sleeve 34 and the bore on the endcap 24 are coaxial and support needle bearing assemblies 38 and 40, respectively. A double ended hollow rotary output shaft 42 is coaxially journalled within the cylinder assembly by the needle bearing assemblies 38 and 40.

The shaft 42 includes an axially elongate shoulder portion 44 having external helical spline teeth 46 disposed within the cylinder sleeve 14. One end of the shoulder 44 is journalled for rotation by a thrust needle bearing assembly 48, and the other end of the shoulder 44 is journalled for rotation by a thrust needle bearing assembly 50. A ring 52 is interposed between the needle bearing assembly 48 and the end of the stationary sleeve 34. A ring 54 is interposed between the needle bearing assembly 50 and the end cap 24.

The annular bulkhead 18 divides the cylinder assembly Ainto two cylinders formed by the sleeves 12 and 14, respectively. An annular piston 56 is disposed within the sleeve cylinder 12 and an annular piston 58 is disposed within the sleeve cylinder 14. The annular piston 56 includes an annular axially extending sleirt 60 having threaded connection at 62 with the piston 58. In 'order to preclude relative rotation between the pistons 56 andl S8, the skirt `60 is also connected to the piston 58 by a radially extending dowel pin 64. Accordingly, the pistons 56 and 58 are rigidly interconnected for simultaneous reciprocation in the same direction. The piston 56 includes a metallic piston ring seal 66 which sealingly en'- gages the inner wall and the sleeve cylinder 12. The bulkhead 18 carries a metallic piston seal 68 which sealingly engages the outer periphery of the piston skirt 60. The piston 58 carries a metallic piston ring seal 70 that 'sealingly engages the inner wall of the sleeve cylinder 14. In addition, the piston 58 has a second metallic piston ring seal 72 engaging the piston skirt 60.

`The piston 56 divides its cylinder into an inboard chamber 74 and an outboard chamber 76. The piston 58 divides its cylinder into an inboard chamber 78 and an outboard chamber 80. The outboard chambers 76 and 80 connect respectively with the ports 28 and 30 in the end caps and 24. The inboard chamber 74 connects with a threaded port openingV 82 in the annular bulkhead 18, and therinboard chamber 78 connects with the threaded port opening 84 in the annular bulkhead 18.

The piston 56 is formed with a set of internal helical spline teeth 86 which mate with the external helical spline teeth 36 on the stationary, or reaction sleeve 34. The piston 58 is likewise formed. with a setof internal helical spline teeth 88 which mate with the external helical spline teeth 46 on the shaft 42. Accordingly, during movement of the tandem arranged pistons 56 and 58 to the left, as viewed in the drawing, the output shaft 42 will be rotated in one direction, for instance, the clockwise direction. On the other hand, upon reciprocation of pistons 56 and 58 to the right as viewed in the drawing, the output shaft 42 will be rotated in the counterclockwise direction. Consequently, the ports and 82 may be termed clockwise rotation ports and the ports 28 and 84 may be termed counterclockwise ports.

The stationary reaction sleeve 34 carriesa pair of spaced metallic piston ring assemblies 90V and 92 which constitute metering orifices that permitjsmall quantities of hydraulic duid to iiow between the piston ring assemblies 90 and 92 and the outer periphery of the shaft 42. This drain flow, utilized for cooling the actuator, is collected in an annular groove that communicates with a drain port 98. The drain fluid is preventedfrom escaping out the left hand end of the shaft 42 by a lowpressure metallic seal assembly 100 held in assembled relation by a nut 102.

The shoulder portion 44 on the shaft 42 carries a pair of piston ring assemblies 104 and 106 which sealingly eng'agethe inner wall of the piston skirt 60. The end cap 24 ycari-'ies a pair of metallic piston ring seal assemblies 108 and 110 likewise constituting metering orifices that permit small quantities of iiuid to flow therepast due to a the piston ring assembiles 108 and 110 is collected in an annular groove 112 having communication with drain port 114. The uid liowing into the groove 112 cannot escape out the right hand end of the shaft 42 due to the low pressure metallic assembly L16 which is held in assembled relation with the end cap 24 by a nut 118.

The arearof the piston 56 exposed to the chamber 76 is substantially equal to the area of the piston 58 exposed to the chamber 80. However, the areas of the pistons 56 and 58 exposed to the inboard chambers 74 and 78, respectively, are slightly less than the areas of the pistons exposed to the outboard chamber by virtue of the skirt 60. In installations where a high torque output is required, the ports 28 and 84 can be interconnected as can the ports 30 and 82. ln so doing, the eifective areas of the pistons is substantially twice that of each piston so that the torque output of the rotary actuator will be substantially twice that of a comparable actuator of the same diameter containing only'a single piston. Where high torque output is not required, the instant actuator provides twin reliability in that the ports 30 and 84 can be connected to one hydraulic system and the ports 28 and 82 can be connected to a normally inactive hydraulic system. Accordingly, upon failure of the normal hydraulic system, the emergency hydraulic system can be used to operate the actuator.

yOperation of the actuator is as follows. When the clockwise port 30 and the clockwise port 82 are connected to pressure and the counterclockwise ports 28 and 84 are connected to drain, the tandem connected pistons 56 and S8 will move to the left, which will be accompanied by an angular movement of the piston due to the interaction of helical spline teeth 86 and 36. The torque on the reaction sleeve is transmitted to the fixed cylinder assembly 10. The angular movement of the pistons will be imparted to the output shaft 42 through the helical spline teeth 88 and 46 such that the output shaft 42 will rotate with a movement which is the sum of that caused by the helical spline teeth 36 and 86, and 88 and 46. vTo impart clockwise movement to the shaft 42, the counterclockwise ports 28 and 84 are subjected to pressure while the counterclockwise ports 30 and 82 are connected to drain.

When the lower torque outputs are required, the clockwise and counterclockwise ports of only one cylinder are connected between pressure and drain whereas the ports of the other cylinder are both connected to drain. When either of the outboard chambers 76 or 80 is subjected to pressure, a metered amount of iiuid will iiow past the piston ring orifices 90 and 92, or 108 and 110, through the drain ports to provide circulating cooling flow for the actuator and the hydraulic system connected thereto.

While the embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

l. A rotary actuator including, a cylinder assembly, means dividing said cylinder assembly into two cylinders, a pair of tandem arranged reciprocable pistons disposed in said cylinders capable of fluid pressure actuation in both directions, a reaction member disposed within one of said cylinders and rigidly connected to said cylinder assembly,

. an output member rotatably journalled in said vcylinder pressure differential. The hydraulic fluid owing past assembly, and helical means interconnecting said pistons and said members whereby reciprocation of said pistons imparts rotation to said output member.

2. A rotary actuator including, a cylinder assembly, an annular bulkhead dividing said cylinder assembly into two cylinders, a pair of tandem arranged reeiprocable pistons disposed in said cylinders capable of fluid pressure actuation in both directions, a reaction member disposed within one of said cylinders and rigidly connected to said cylinder assembly, and an output member rotatably journalled in saidcylinder assembly, said members having external helical means, said pistons having internal heliannular bulkhead dividing said cylinder assembly into twoV cylinders, a pair oftandem arranged reciprocable pistons disposed in said cylinders capable of fluid pressure actuation in both directions, a reaction member rigidly connected to said cylinder assembly and having a set of external spline teeth disposed within one of said cylinders, and an output member rotatably journailed in said cylinder assembly and having a set of external helical spline teeth disposed within the other cylinder, said pistons having sets of internal helical spline teeth mating with the sets of external helical spline teeth on said member whereby reciprocation of said pistons imparts rotation to said output member. ,l

4. A rotary actuator including, a cylinder assembly comprising a pair of spaced end caps, a pair of sleeves attached to said end cap yand an intermediate annular bulkhead attached to said sleeves and dividing said cylinder assembly into two cylinders, a pair of tandem arranged reciprocable pistons disposed in said cylinders capable of fluid pressure Iactuation in both directions, an annular reaction member disposed within one of said cylinders and rigidly connected to said cylinder assembly, an annular output member rotatably journalled in said cylinder assembly and coaxial with said annular reaction member,

and helical means connecting said pistons and said members whereby reciprocation of said pistons imparts rotation to said output member.

5. The rotary actuator set forth in claim 4 wherein each piston divides its cylinder into opposed chambers, wherein each end cap has a port communicating with one chamber of each cylinder, and wherein said annularbulkhead has a pair of ports, one of which communicates with the opposed chamber of each cylinder.

6. The rotary actuator set forth in claim 5 wherein one of said pistons includes an axially extending annular skirt which extends through and is sealingly engaged by said annular bulkhead, and means rigidly attaching the skirt of said one piston to the other piston.

7. The rotary actuator set forth in claim 4 wherein said rotary output member extends from both sides of said cylinder assembly, and wherein each end cap carries bearing means for rotatably supporting said output member.

y 8. A uid pressure operated rotary actuator, including, a cylinder assembly, an annular bulkhead dividing said cylinder assembly into a pair of cylinders, an annular piston disposed within each cylinder capable of fluid pressure actuation in both directions, an output member rotatably supported in said cylinder assembly, means rigidly interconnecting said pistons for simultaneous movement in the same direction, and a sleeve rigidly connected to said cylinder assembly and having external helical spline teeth, said output member having external helical spline teeth, each piston having internal helical spline teeth, the helical spline teeth on one of said pistons mating with the helical spline teeth on said sleeve and the helical spline teeth on the other piston mating with the helical spline teeth on said output member whereby reciprocation of said pistons will impart rotation to said output member.

9. A rotary actuator assembly including, a cylinder assembly, an annular bulkhead dividing said cylinder assembly into a pair of cylinders, -a pair of tandem arranged reciprocable pistons disposed in said cylinders, an output member rotatably journalled in said cylinder, a stationary reaction member attached to said cylinder assembly and having a helical spline connection with one of said pistons, and a helical spline connection between the other piston and said output member for impartingrotation thereto upon reciprocation of said pistons.

Reerences Cited in the le of this patent UNITED STATES PATENTS 1,776,228 Coffman Sept. 16, 1930 2,688,951 Sears Sept. 14, 1954 2,747,549 Gerry et al May 29, 1956 2,765,778 Gerry et a1. Octt9, 1956 2,791,128 Geyer et al. May 7, 1957 FOREIGN PATENTS 201,107 Australia Feb. 17, 1956 

